Process for producing protected metal surfaces



Nov. 3, 1964 P. E. SCHNEDLER 3,155,530

PROCESS FOR PRODUCING PROTECTED METAL SURFACES Filed May 25, 1959 I N VEN TOR. Pa/L farm/ea Jay/mm EK A T RNEYS.

United States Patent Filed May 25, 1959, Ser. No. 815,636 8 Claims. (Cl. 117-17) This invention has to do with protected metal articles, and more particularly to a coated metal article, such as zinc coated steel, the coated surface of which is protected by a covering of fibrous material.

It has hitherto been proposed to protect a metal article such as a sheet or strip, coated with tin, zinc, aluminum, lead, or other similar metals or alloys having a lower melting point than steel, by means of a web of fibrous material pressed into the coating metal while the latter is a fluid state. It has been variously proposed to bond a web of asbestos felt to a coated steel strip as an adjunct of the coating operation, i.e., the felt fed into contact with the strip as it emerges from the coating pot; by assembling the coated sheet and the felt layer and placing the assembly in an oven to at least soften the coating, whereupon the felt is pressed into the softened coating so that when the coating cools, the felt layer will be adhesively bonded to the coating; and by initially permitting the coating metal to solidify on the steel strip and thereafter rapidly heating the strip, as by induction or radiant heating, and immediately bringing the felt material into contact with the softened coating, whereupon the coating is permitted to solidify and bond to the fibrous layer.

All of the foregoing procedures have the disadvantage of relatively high cost, and some have the limitation of intermittent sheet operation. The resultant products have the disadvantage of very limited formability because of cracking of the fibrous layer and the separation of the fibrous layers when in tension.

A principal use of such fibrous covered sheets is in the manufacture of metal conduits, such as culverts and the like, wherein the fibrous layer serves as a base or bonding medium for an asphalt coating which Waterproofs the structure and protects it against the corrosive action of water, acids and the like. A satisfactory asphalt to metal bond cannot be obtained; and it is for this reason that a fibrous layer is provided. However, with conventional fibrous layers applied in the ways characterized hereinbefore, unreliable saturating characteristics are encountered together with water leakage along the fibrous layer. These disadvantages, coupled with the limited formability of the fibrous web and its tendency to delaminate or separate into plies, very often lead to premature failure of the product.

In view of the foregoing, it is a principal object of the instant invention to provide an improved product which has lower cost, better asphalt saturation and water resistance, and superior formability, together with apparatus and procedures which permit uninterrupted production.

A further object of the invention is the provision of a procedure whereby particles of fibrous material, such as short fiber asbestos, are propelled as such against the molten coating metal with such force that the metal oxide film on the surface of the coating is penetrated 3,155,536 Patented Nov. 3, i964 thereby causing the fibers to be entrapped by the coating metal as it subsequently solidifies.

Still a further object of the instant invention is the provision of an improved metal coated article having a protective layer composed of discrete fibers or particles embedded in the coating metal, to form a protective covering to which a saturant, such as aphalt, will readily bond.

Still a further object of the invention is the provision of apparatus capable of producing protected metal articles of the character herein contemplated.

Thet foregoing objectives together with others which will appear hereinafter or which will be apparent to the skilled worker in the art upon reading these specifications, are accomplished by those procedures and by that apparatus of which an exemplary embodiment shall now be described, reference being had to the accompanying drawing in which the single figure is a diagrammatic view of an apparatus for practicing the instant invention.

Preferably, the invention will be carried out as an adjunct of the coating operation, the steel strip being passed through the usual coating pot or other coating apparatus and then led immediately into the apparatus of the instant invention wherein flocking guns spray the fibers directly onto the unsolidified coating metal. Of course, if desired, a sheet or strip which has been previously coated, and on which the coating has solidified, could be reheated and the fibers sprayed into the softened coating.

In accordance with the preferred procedure, a strip of steel 1 will be led into the conventional coating pot 2 where it will pass around pot roll 3 and upwardly between exit rolls 4, all as will be readily understood by the skilled worker in the art, the pasage of the strip through the coating pot serving to coat the surfaces of the strip with the desired amount of coating metal. The construction and arrangement of the coating pot does not constitute a limitation on the invention and consequently it may take any desired form consistent with the provision of a suitably coated strip.

Similarly, the coating metal itself does not constitute a limitation on the invention, and while molten zinc will probably be the most commonly used coating metal, the instant invention is equally applicable to other metallic coatings, such as aluminum, tin, lead, and similar metals and alloys thereof.

Immediately upon emerging from the coating bath, the strip is continuously advanced into an elongated, pref stably vertically disposed, spray chamber 5 having flocking spray guns 6 located near the bottom or entrance end thereof and positioned to cause the fibrous material to impinge upon the coated surface of the sheet. It will be understood, of course, that one or both sides of the strip may be sprayed, and that the number of nozzles employed may be varied as required to provide the desired coverage.

The fibrous material will be supplied to the spray guns 6 from one or more hoppers 7 preferably provided with screw-type conveyors 8 rotating inside the hoppers 7. The fibers will be propelled into the molten coating metal by air pressure supplied to the spray guns or nozzle 6 through conduits 9 connected to a suitable source of air under pressure (not shown).

The fibers themselves do not constitute a limitation on the invention, and While asbestos fibers of short length designated comercially as 6D are preferred where the protected sheet is to be subsequently coated with asphalt, other fibrous materials, such as rock wool or glass wool may be employed, or non-fibrous materials as diatomaceous earths or other solid particles. The principal requisites of such fibers or particles are chemical inertness and the ability to be accelerated sufiiciently to penetrate the surface of the molten coating metal.

For good adhesion it is necessary that the fibers or particles being embedded in the molten coating metal have sufficient mass and velocity so that their resultant momentum is sufficiently great to penetrate the surface ilm of the coating metal. If the particle or fiber mass is too small, velocity must be increased to a point where the molten metal is disturbed or even blown off by the air blast. Best results have been obtained with a dense, short-fibered material, such as the aforementioned 6D asbestos fibers.

In an exemplary embodiment utilizing asbestos fibers of short length, highly satisfactory results have been obtained utilizing 100200 p.s.i. air pressure with the spray nozzles positioned about 6" from the surfaces of the strip. Where these conditions exist, it has been found that sufficient momentum is imparted to the fibrous particles to cause them to impinge upon the coating metal with such force that the metal oxide film on the surface is penetrated, thereby causing the fibers to be entrapped by the coating metal as it solidifies.

After being coated with fibers, the molten coating metal will be permitted to solidify, whereupon the strip is brought into contact with rotating brushes 1% located near the top or exit end of the chamber 5, such brushes acting to remove excess fibers. Such surplus fibers are then removed from the spray chamber by means of one or more suction fans 11 having intake conduits 12 in communication with the lower end of the spray chamber, and outlet conduits 13 which serve to return the surplus fibers to the hoppers 7 for reuse.

As the coated strip emerges from the spray chamber 5, and while it is still at a temperature of from 200500 F., depending on the nature of the coating metal, it is preferred to apply a fast-drying saturant, such as asphaltum paint thinned with naphtha, to permit the material to be subsequently handled without sticking or loss of fibers. Other suitable saturants, such as the primers for various types of organic finishes, may be readily substituted for the asphaltum. In any event, the residual heat of the strip results in fast drying of the saturant. The application of such saturant is diagrammatically indicated by the spray nozzles 14, although other types of applicators could be employed, such as coating rollers.

As should now be apparent, the procedures just described result in the provision of a fiber protected coated steel article in which the individual fibers are embedded in and entrapped by the coating metal. By reason of the fact that the fibers or particles are discrete and individually secured to the coating, the resultant product can be readily formed, even at acute angles, without materially disrupting the protective layer so formed. The problem of delamination or separation of the plies of a fibrous web is eliminated; and the protruding fibers provide an excellent base for the subsequent application of asphalt or other coating materials. The apparatus is both simple and economical, as is the procedure itself, and materail savings are effected both in time and labor.

Of course, it will be understood that subsequent to the application of the fibrous layer, the article will be coated with asphalt, pitch, tar or other coating material which firmly bonds to the fibrous layer and provided a protective surface coating for the article. Such asphalt or like coating may be applied either before or after the fabrication of the article.

It will be clear that numerous modifications may be made without departing from the spirit of the invention. For example, while it is preferred to apply the fibers or particles by means of flocking spray guns, such particles could be applied by means of centrifugal force. It is also contemplated that the fibers may be oriented by propelling them in an electrostatic field, as by means of an electrostatic generator 15, having one pole 16 connected so as to charge the particles or fibers to be propelled, while the opposite pole or ground 17 of the generator 15 is connected to the strip through the bath of molten metal in the pot 2. Similar modifications will undoubtedly occur to the skilled worker upon reading these specificaitons, and consequently it is not intended that the invention be limited otherwise than as set forth in the claims which follow. In reading the claims, it is to be understood that the terms fibers and fibrous material as employed therein contemplate not only materials such as asbestos and the like which are truly fibrous in character, but also other types of palticles, inclusive of such non-fibrous materials as diatomaceous earths, which may be utilized to provide a protective layer or covering for a coated steel strip or sheet.

Having now fully described the invention, what is claimed as new and desired to be protected by Letters Patent is:

l. A method of producing a protected metal article having a fibrous material affixed to a base sheet by an interposed metallic coating, which comprises directing a spray of individual fibers against the metallic coating while the latter is in a heated condition and sufficiently fluid so that the fibers impinging thereon will be at least partially embedded in said metallic coating, and thereafter allowing the metallic coating to cool.

2. The method claimed in claim 1 wherein said fibers are sprayed against said metallic coating by means of air under pressure.

3. The method claimed in claim 1 wherein, subsequent to the cooling of said metallic coating, the fibrous material embedded therein is acted upon by brushes serving to remove excess fibers.

4. A method of providing a protected metal article comprising a continuous strip of ferrous metal having a non-ferrous metallic coating thereon, which comprises advancing said ferrous strip in a path of travel and, while the metallic coating thereon is in a heated and substantially fluid condition, propelling particles of fibrous material against the surface of the metallic coating with such force that the surface of the coating is penetrated, whereby to cause the fibrous material to be entrapped by the metallic coating metal as it subsequently solidifies.

5. The method claimed in claim 4 wherein the fibrous material is propelled against the metallic coating in an electrostatic field.

6. The method claimed in claim 4 wherein, subsequent to the application of the fibrous material to the metallic coating, any excess, loosely adherent material is removed by brushing at a time when the metallic coating has solidified.

7. The method claimed in claim 4 wherein, subsequent to the application of the fibrous material and the solidification of the metallic coating, a fast-drying saturant is applied to the fibrous material.

8. A method of producing a protected metal article having a fibrous layer composed of discrete fibers affixed to a metal base member by an interposed metallic layer of lower-melting point than said metal base member, which comprises propelling the said discrete particles against the metallic layer of lower-melting point while the latter is in a substantially molten condition, said fibers being of relatively short length and propelled at a velocity such that the momentum of the fibers is sufiiciently great to penetrate the surface of the metallic layer, whereby upon subsequent solidification of the metallic layer, said fibers will be at least partially embedded therein and entrapped.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Meuer Oct. 16, 1928 Cofiman Mar. 9, 1937 Snyder Jan. 1, 1946 Mincieli Apr. 12, 1949 Comstock Jan. 31, 1950 Hansell June 27, 1950 6 Le Sech Dec. 14, 1954 Colfman Nov. 22, 1955 Toulmin Feb. 7,1956 Stewart June 4, 1957 OTHER REFERENCES 

4. A METHOD OF PROVIDING A PROTECTED METAL ARTICLE COMPRISING A CONTINUOUS STRIP OF FERROUS METAL HAVING A NON-FERROUS METALLIC COATING THEREON, WHICH COMPRISES ADVANCING SAID FERROUS STRIP IN A PATH OF TRAVEL AND, WHILE THE METALLIC COATING THEREON IS IN A HEATED AND SUBSTANTIALLY FLUID CONDITION, PROPELLING PARTICLES OF FIBROUS MATE- 